title: CRP interacts with promoter-bound sigma54 RNA polymerase and blocks transcriptional activation of the dctA promoter.
abstract: The cAMP receptor protein (CRP) is an activator of sigma70-dependent transcription. Analysis of the sigma54-dependent dctA promoter reveals a novel negative regulatory function for CRP. CRP can bind to two distant sites of the dctA promoter, sites which overlap the upstream activator sequences for the DctD activator. CRP interacts with Esigma54 bound at the dctA promoter via DNA loop formation. When the CRP-binding sites are deleted, CRP still interacts in a cAMP-dependent manner with the stable Esigma54 closed complex via protein-protein contacts. CRP is able to repress activation of the dctA promoter, even in the absence of specific CRP-binding sites. CRP affects both the final level and the kinetics of activation. The establishment of the repression and its release by the NtrC activator proceed via slow processes. The kinetics suggest that CRP favours a new form of closed complex which interconverts slowly with the classical closed intermediate. Only the latter is capable of interacting with an activator to form an open promoter complex. Thus, Esigma54 promoters are responsive to CRP, a protein unrelated to sigma54 activators, and the repression exerted is the direct result of an interaction between Esigma54 and the CRP-cAMP complex.
authors.affiliation: Unité de Physicochimie des Macromolécules Biologiques (URA1149 du CNRS), Institut Pasteur, 75724 Paris cedex 15, France.
authors.forename: Y P
authors.initials: YP
authors.lastname: Wang
authors.forename: A
authors.initials: A
authors.lastname: Kolb
authors.forename: M
authors.initials: M
authors.lastname: Buck
authors.forename: J
authors.initials: J
authors.lastname: Wen
authors.forename: F
authors.initials: F
authors.lastname: O'Gara
authors.forename: H
authors.initials: H
authors.lastname: Buc
mesh_terms: D001426:Bacterial Proteins; D001665:Binding Sites / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D002352:Carrier Proteins / Q000235:genetics*; D000242:Cyclic AMP / Q000494:pharmacology; D002373:Cyclic AMP Receptor Protein / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D004268:DNA-Binding Proteins / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D029382:Dicarboxylic Acid Transporters; D004347:Drug Interactions; D004742:Enhancer Elements, Genetic / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000502:physiology; D007700:Kinetics; D011401:Promoter Regions, Genetic / Q000235:genetics* / Q000502:physiology; D011485:Protein Binding / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D012808:Sigma Factor / Q000235:genetics; D015533:Transcriptional Activation / Q000235:genetics / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D002373:Cyclic AMP Receptor Protein; D004268:DNA-Binding Proteins; D029382:Dicarboxylic Acid Transporters; D012808:Sigma Factor; C073786:dctA protein, Sinorhizobium meliloti; D000242:Cyclic AMP; D012321:DNA-Directed RNA Polymerases